Europium fluorescence is significantly enhanced through ligand sensitization using aromatic benzene mono and di carboxylic acids as ligands in aqueous solution. By optimising metal to ligand ratio and solution pH, it is established that the enhancement is maximum with isophthalic and terephthalic acid. Phosphorescence of isophthalic acid is recorded and its triplet energy level is found to be at 25633 cm-1; just above the fluorescing energy level of Eu3+. On complexation with these ligands though the europium luminescence is enhanced by orders of magnitude, the europium lifetime increased marginally. Addition of picric acid resulted in the quenching of europium luminescence in europium-isophthalic acid complex. Based on this quenching, a fluorimetric method is developed for the estimation of picric acid in aqueous solution. Picric acid in aqueous solution could be estimated down to 0.23 ppm. Common cations and anions found in natural waters did not interfere in the analysis. The precision in measurement is within 5% RSD in the entire range of measurement.

中文翻译：

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用于检测苦味酸的镧系发光探针

通过使用芳香苯单羧酸和二羧酸作为水溶液中的配体的配体敏化，铕荧光显着增强。通过优化金属与配体的比例和溶液 pH 值，可以确定间苯二甲酸和对苯二甲酸的增强作用最大。记录间苯二甲酸的磷光，发现其三线态能级为 25633 cm-1；略高于 Eu3+ 的荧光能级。在与这些配体络合时，虽然铕发光增强了数量级，但铕寿命略有增加。添加苦味酸导致铕-间苯二甲酸配合物中铕发光的猝灭。基于这种猝灭，开发了一种用于估计水溶液中苦味酸的荧光法。水溶液中的苦味酸可估计低至 0.23 ppm。在天然水中发现的常见阳离子和阴离子不会干扰分析。在整个测量范围内，测量精度在 5% RSD 以内。